The effect of sugars on the extrusion of maize grits: II. Starch conversion

Differential scanning calorimetry (DSC), X-ray diffraction and rheological studies have revealed that the conversion of A-type starch during the extrusion of mixtures of maize grits with sugars depends on sugar type and concentration. Sugars inhibited the starch conversion (fructose more than sucrose) by reducing the specific mechanical energy input. Addition of sugars led to changes in the packing of amylose–lipid complexes in the extrudate from an E-type to V-type. It is postulated that the complexes pack initially in the less stable E-form and then rearrange to the more stable V-form, a process which is accelerated by the addition of sugars because of the enhanced molecular mobility resulting from the reduction in the glass transition temperature. This rearrangement is also seen when extrudates containing no sugar are equilibrated at ambient temperature at moisture contents between 14.5% and 18% (w.b.).     

Formation of amylose complexes with C6-aroma compounds in starch dispersions and its impact on retention

Interactions between aroma compounds and starch matrices may increase the retention of aroma compounds. In particular, the linear amylose of starch, is able to form inclusion complexes with a wide variety of flavour compounds.     

X射线衍射测定淀粉颗粒结晶度的研究进展

详述了国内外有关X射线衍射测定淀粉颗粒结晶度方法的研究进展以及应用。其中介绍了Herman、Wakelin,Nara和张本山等用X-射线衍射测定结晶度的不同方法,并分析比较了这几种方法的测定原理、优缺点,以及几种常见淀粉颗粒的结晶度。最后,对X射线衍射测定淀粉颗粒结晶度方法改进进行了展望。     

抗性淀粉结晶性质的研究

本文利用X-射线衍射分析法确认了各抗性淀粉中晶体的存在。结果表明,样品重新结晶效果好,结晶度比原淀粉有所提高,总结晶度及不同类型微晶含量与抗性淀粉含量呈现一定规律性:处理条件相差不大的样品,其结晶度越大,抗性淀粉含量越高,而且它们的高级微晶含量也呈现同样规律性;经完全不同条件处理的样品则不符合此规律。高级微晶与初级微晶仅根据晶体粒度大小来划分,并非高级微晶的牢固紧密程度一定大于初级微晶。     

Formation of Supramolecular Structures of Aroma Compounds with Polysaccharides of Corn Starch Cryotextures

The binding absorption of individual alcohols, ketones, alkyl acetates and their mixtures — used as aroma compounds — from aqueous solutions by corn starch cryotextures was studied by capillary gas chromatography at different starting concentrations of the odourants (1—25 mmol/L). The amount of compound sorbed by the cryotextures increases with concentration of this compound in the initial sol and increasing length of the alkyl chain in the corresponding compound. Linear equations describing the concentration dependence were proposed. The presence of octanol in the mixture increases the binding of hexanol as compared to hexanol alone. The methods of scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy, differential scanning microcalorimetry (DSC) and scanning tunneling microscopy (STM) were used for estimation of the microstructure of sols, and cryotextures, and for the determination of supramolecular complex formation in the systems odourant/cryotexture and odourant/sol. It was shown that waxy corn cryotextures do not form supramolecular complexes with aroma compounds.     

离子液体中酶催化合成硬脂酸淀粉酯及其流变学特性研究

以1-丁基-3-甲基咪唑醋酸盐（[BMIM]Ac）和1-丁基-3-甲基咪唑四氟硼酸盐（[BMIM]BF4）的混合离子液体为介质,脂肪酶催化淀粉硬脂酸甲酯合成硬脂酸淀粉酯,并采用核磁共振（1H NMR）、X-射线衍射对其进行结构表征。通过快速黏度仪及动态流变仪分析了硬脂酸淀粉酯的流变学特性。结果表明:和原淀粉相比,硬脂酸淀粉酯的峰值黏度显著降低,并随着取代度的增大,黏度呈下降趋势;动态流变学测定结果显示酯化后的淀粉储能模量和损失模量比原淀粉显著下降（p<0.05）;静态流变学测定结果显示淀粉（包括酯化淀粉）为非牛顿流体,出现了剪切稀化的现象,且取代度越高,黏度越低,表明长链硬脂酸基团的引入,削弱了淀粉分子之间氢键作用。      

湿热处理对甘薯淀粉流变特性的影响

目的:采用HAAKE MARSⅢ型流变仪研究不同湿热处理条件下甘薯淀粉的流变性。方法:通过控制湿热处理的水分(10%~30%)、温度(90~130 ℃)和时间(4~12 h)对甘薯淀粉进行湿热改性。结果:原淀粉与湿热改性淀粉的糊具有明显的剪切稀化行为,其流变曲线也服从Herschel-Bulkley模型。不同湿热处理条件下得淀粉糊浓度系数K、屈服应力τ₀均低于原淀粉(K_原=14.816 Pa·sⁿ,τ_0原=10.322 Pa),流动特性指数n高于原淀粉(n_原=0.47)。随着湿热处理水分、温度与时间的增加,淀粉糊的K逐渐减小,τ₀则先增后减,湿热处理水分20%,温度110 ℃,时间8 h的屈服应力最大(τ_0上行线=5.683 Pa,τ_0下行线=12.423 Pa)。动态流变学特性表明:不论湿热改性与否,甘薯淀粉糊的储能模量(G')均大于损耗模(G″)。并且相对于原淀粉,湿热改性甘薯淀粉糊的黏弹性明显增加。结论:经过湿热处理,甘薯淀粉糊的浓度系数与屈服应力下降,非牛顿性减弱,黏弹性显著提高,更适合作为食品加工的辅料和添加剂。     

橡实淀粉多晶体系结晶度测定

运用广角X-射线衍射分析方法对橡实淀粉的结晶结构进行了系统研究,结果表明：橡实淀粉粒是一种由非晶相、亚微晶相和微晶相三种结构所组成的多晶体系,其结晶度分别为锥栗淀粉34．88％、茅栗淀粉35．12％、小红拷淀粉35．23％、栓皮栎淀粉35．31％、硬斗石栋淀粉33．53％、星毛石砾淀粉34．69％、美叶石栋淀粉35．06％、长叶石烁淀粉31．58％、云山青冈淀粉33．83％、大叶青冈淀粉32．11％。     

Characterization of the key aroma compounds in beef extract using aroma extract dilution analysis

Aroma extract dilution analysis (AEDA) of an ether extract prepared from beef extract (BE) and subsequent identification experiments led to the determination of seven aroma-active compounds in the flavor dilution (FD) factor range of 32–128. Omission experiments to select the most aroma-active compounds from the seven aroma compounds suggested that 2,3,5-trimethyl pyrazine, 1-octen-3-ol, 3-methylbutanoic acid, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone were the main active compounds contributing to the aroma of BE. Aroma recombination, addition, and omission experiments of the four aroma compounds in taste-reconstituted BE showed that each compound had an individual aroma profile. A comparison of the overall aroma between this recombination mixture and BE showed a high similarity, suggesting that the key aroma compounds had been identified successfully.     

Characteristics of Imitation Cheese Containing Native Starches

ABSTRACT Imitation cheeses containing 3% native maize, waxy‐maize, wheat, potato or rice starch were manufactured and the microstructure, meltability, texture and dynamic rheology of these products were compared to a control (0% starch). Fat globules in starch‐containing products (except potato) were smaller than in the control as evidenced by electron microscopy. All starches reduced meltability and cohesiveness of the imitation cheeses. Hardness was increased by wheat, potato or maize starch but reduced by waxy‐maize or rice starch. Starches significantly reduced tan 8 peaks compared to the control with potato starch having the greatest effect. Rice starch appears to have the most potential as a partial casein substitute in imitation cheese.     

Interaction between starch and aroma compounds as measured by proton transfer reaction mass spectrometry (PTR-MS)

The interaction between starch and the complexing aroma compounds hexanal and menthone was investigated by headspace analysis using proton transfer reaction mass spectrometry (PTR-MS). Starch systems with non-modified and modified tapioca starch were prepared containing single aroma compounds (hexanal, menthone) or a blend of the two aroma compounds at low aroma concentrations (6 × 10⁻³ mg/100 g). The headspace intensity of starch–aroma systems was slightly reduced due to starch–aroma interactions compared to aroma water-systems. The combination of hexanal and menthone did not lead to competitive aroma release effects, but hexanal retention increased by increasing the equilibration time from 48 to 96 h. Non-modified and chemically modified starch showed similar aroma release behaviour. It is concluded that the formation of starch–aroma complexes influences aroma release, but that at low aroma concentration the dissociation of the complex is not hindered by the aggregation of amylose–aroma complexes.     

小麦淀粉的超高压糊化研究

5%的小麦淀粉悬浮液在400MPa、450MPa、500MPa、550MPa压力下处理5min后,再经过干燥处理,所得到的样品用偏光显微镜和X-射线衍射技术对其进行测定,结果表明：经450MPa压力作用后,小麦淀粉已经发生了明显的溶胀;500MPa及其更高的压力作用后,小麦淀粉已经被完全糊化;常温下5%浓度时,小麦淀粉的糊化压力范围为400～500MPa。     

介质对超高压改性玉米淀粉的影响

分别选用浓度为5%(w/v)的蔗糖、CaCl2、Na2HPO4和NaCl溶液作为淀粉悬浮介质,在570MPa压力下对5%(w/v)的玉米淀粉悬浮液进行高压处理5min,应用偏光显微镜和X-射线衍射仪检测所得样品的结晶性能和结构变化,结果表明:介质对玉米淀粉结构的影响能力从大到小的顺序为5%蔗糖>5% Ca-Cl2>5% Na2HPO4>5% NaCl;5% CaCl2和5% NaCl可以提高处理后的淀粉的结晶度。     

基于X-射线衍射及扫描电子显微镜的马铃薯淀粉掺伪鉴别

目的建立一种快速、准确鉴别市售马铃薯淀粉掺伪的方法。方法将红薯、玉米及小麦淀粉按不同比例加入纯马铃薯淀粉中,通过X-射线衍射(X-ray diffraction,XRD)对样品进行结晶结构分析,并结合扫描电子显微镜(scanning electron microscope,SEM)进行微观形貌观察。结果利用结晶类型差异,XRD可初步判别马铃薯淀粉样品是否掺入上述3种淀粉,进一步采用SEM可观察到含量1%的掺伪淀粉并对其种类进行区分。在市售12批次马铃薯淀粉中的7批次中发现存在掺伪现象,其中2批次利用扫描电镜未观察到马铃薯淀粉(小于1%)。结论市售马铃薯淀粉掺伪现象严重,利用X-射线衍射及扫描电子显微镜可快速、准确地鉴别马铃薯淀粉掺伪情况。     

促进玉米直链淀粉回生的甘薯淀粉晶种的筛选及表征

通过向四次回生的玉米直链淀粉中添加草酸侵蚀的四次回生的甘薯淀粉、甘薯直链和甘薯支链淀粉晶种(质量分数:1%),研究甘薯淀粉晶种对玉米直链淀粉回生的影响。结果表明,甘薯淀粉晶种明显促进了玉米直链淀粉回生长晶,其中甘薯直链淀粉晶种使得玉米直链淀粉回生率达到59.5%,比不添加晶种提高了19.3%。可见吸收光谱研究表明,甘薯淀粉晶种及长晶后的玉米直链淀粉均保持了双螺旋结构。X-射线研究表明草酸侵蚀后甘薯淀粉、甘薯直链淀粉、甘薯支链淀粉均为A+B型。将其分别添加到玉米直链淀粉中并长晶后的样品,结构均为B型。DSC研究表明,甘薯支链淀粉晶种具有最高的吸热焓,说明其晶体含量最高。三种晶种分别促进玉米直链淀粉长晶后的结构较为相似,晶体含量也较相近。该研究为提高淀粉的回生率、研究回生淀粉结晶结构提供良好的技术支持。